The High Efficiency Video Coding (HEVC) standard, a next-generation image coding standard, has been examined in various ways to increase its coding efficiency (Non Patent Literature (NPL) 1). In addition, the International Telecommunication Union Telecommunication Standardization sector (ITU-T) standard typified by H.26x, and the ISO/IEC standard typified by MPEG-x exist conventionally. The latest and most advanced image coding standard has been examined as a standard next to a standard currently typified by H.264/AVC or MPEG-4 AVC (see Non Patent Literature (NPL) 2).
In the HEVC standard, coding degradation reduction processing referred to as sample adaptive offset (SAO) has been examined to further reduce coding degradation (a difference between an original signal before coding and a coded and decoded signal). The SAO is offset processing in which an offset value is added for each of predetermined regions, categories, or types, to reduce the coding degradation, and is performed on a provisionally decoded image (reconstructed image) (see Non Patent Literature (NPL) 3).